Avissar S, Amitai G, Sokolovsky M
Proc Natl Acad Sci U S A. 1983 Jan;80(1):156-9. doi: 10.1073/pnas.80.1.156.
The potent muscarinic photoaffinity reagent N-methyl-4-piperidyl p-azidobenzilate (azido-4NMPB) was used to covalently label specific muscarinic binding sites in various brain regions and in the heart. In the cortex and hippocampus, a single specifically labeled protein with an apparent molecular mass of 86,000 daltons was detected by gel electrophoresis. In the medulla pons, cerebellum, and cardiac atria, there was a 160,000-dalton band in addition to the 86,000-dalton polypeptide. Under certain conditions, alkali or hydroxylamine treatment dissociated both macromolecules into a single 40,000-dalton polypeptide. These results suggest that the muscarinic receptor exists in oligomeric forms and that a dimer and tetramer of a basic 40,000-dalton peptide may exist as interconvertible species. We propose a model to explain the biological architecture of the muscarinic receptors and suggest a possible correlation between the azido-4NMPB-labeled polypeptides and the two states of the receptor observed in agonist binding experiments.
强效毒蕈碱光亲和试剂N-甲基-4-哌啶基对叠氮苯甲酸酯(叠氮基-4NMPB)被用于共价标记不同脑区和心脏中的特定毒蕈碱结合位点。在皮质和海马体中,通过凝胶电泳检测到一种表观分子量为86,000道尔顿的单一特异性标记蛋白。在延髓脑桥、小脑和心房中,除了86,000道尔顿的多肽外,还有一条160,000道尔顿的条带。在某些条件下,碱或羟胺处理会使这两种大分子解离成单一的40,000道尔顿多肽。这些结果表明毒蕈碱受体以寡聚体形式存在,并且一种基本的40,000道尔顿肽的二聚体和四聚体可能以可相互转化的形式存在。我们提出一个模型来解释毒蕈碱受体的生物学结构,并提出叠氮基-4NMPB标记的多肽与激动剂结合实验中观察到的受体两种状态之间可能存在的相关性。